Significant efforts are being devoted to development of durable metal-carbon based materials for use as electrodes in lithium-ion batteries. Generally, the effective life of these electrodes is limited by the pulverization of these particles due to the high volumetric change during lithiation and delithiation cycles, which leads to particles pulverization and destabilization of solid electrolyte interphase (SEI) films, resulting in fast capacity fading and low Coulombic efficiency.
Much effort has been focused on creating conductive metal oxide/graphene composites, structured in such a fashion that the metal oxides are physically prevented from crumbling. For example, there are many studies focused on Fe3O4 mixed/fixed on different conductive forms of carbon because iron oxide not only has a potentially high maximum capacity, 922 mAh/g, but also meets conductivity, cost and environmental objectives. This is far better than that of the graphite electrode, 372 mAh/g, due to the final Stage 1 structuring Li/C stoichiometry of LiC6. Another material, with an even higher ‘theoretical’ capacity, lower operating potential than metal oxides for enhanced full cell energy density, and decreased voltage hysteresis due to the alloying storage mechanism, is metallic Sn. The final stoichiometry of Li/Sn, Li22Sn5 has a high lithium packing density (75.47 mol L−1), which is nearly as high as that of pure lithium metal (76.36 mol L−1). This packing density yields a theoretical ˜990 mAh/g for Sn. However; like the other alternatives to graphite, Sn is not employed because of the mechanical pulverization which leads to rapid deterioration of capacity with cycling. In particular, Sn expands so significantly (˜360%) during lithiation, and then shrinks during charging, that it physically pulverizes during cycling, creating an unstable and unusable electrode. Specifically, disintegration leads to a rapid drop in capacity with cycling and excessive solid electrolyte interphase (SEI) formation, rapidly consuming electrolyte and increasing electrode resistance. As with magnetite, novel approaches to mitigate the crumbling that accompanies expansion during lithiation have been tried. For example, the encapsulation of Sn within nano-scale conductive carbon structures, with void space to accommodate expansion without concomitant breakage, yields high initial capacity, and improved, but still not sufficient, stability with cycling. Additionally, scalable fabrication and material cost are also the key issues for practical application of energy storage devices.
It would be advantageous to provide a rapid synthesis process for the generation of a heterogeneous carbon-bonded material using materials which are standard and inexpensive. This would offer significant economic advantages over other more intricate synthetic approaches requiring expensive/exotic materials. It would be particularly advantageous if a variety of species such silicon (Si), germanium (Ge), and tin (Sn) considered potentially valuable for creating high capacity Li ion battery anodes could be produced as small, stable particles on relatively inexpensive forms of carbon.
These and other objects, aspects, and advantages of the present disclosure will become better understood with reference to the accompanying description and claims.